Synchronous Optical Network (SONET) is a standard for multiplexing data. It is used primarily for backbones composed of fiber optics. SONET performs a complicated timing and multiplexing scheme. It uses certain signaling levels called “Synchronous Transport Signals” or STS. Each STS level corresponds to a specification of “Optical Carriers.” Due to its complexity, the equipment needed to operate a SONET network is extremely expensive. SONET networks power some of the world's networks (telephone and Internet). For that reason, SONET is designed to run at 99.999% uptime. This is also known as “the 5 nines” of availability.
One of SONET's interesting characteristics is its support for a ring topology. Normally, one piece of fiber or “working ring” handles all data traffic, but a second piece of fiber or the “protection ring” remains on standby. Should the working ring fail, SONET includes the capability to automatically detect the failure and transfer control to the protection ring in a very short period of time. For this reason, SONET can be described as a self-healing network technology.
Many of the functions of a SONET network and SONET rings operate at or with a physical layer or the layer of the fiber optic cabling. The Internet Protocol or IP protocol utilizes the concept of a ring such as a token ring, but the IP rings operate at a much higher layer in the open systems interconnect (OSI) model.
Given the present state of the art, a need arises for a resilient IP ring protocol and architecture.